Magnetic transducer with a write head having a multi-layer coil

ABSTRACT

Applicants disclose a method for producing a magnetic transducer with a inductive write head having a multilayer coil with a high aspect ratio and a short yoke. A damascene process is used for two coil layers and a conventional process for the third coil layer. The process of the invention allows a seed layer for the coil to be deposited on the side walls of the trenches for the first and second coil layers. In one embodiment the seed layer for the coil is preceded by an adhesion layer.

RELATED APPLICATIONS

[0001] This is a divisional application currently pending applicationbearing Ser. No. 10/279169 which was filed on Oct. 23, 2002.

[0002] Pending U.S. patent application published as US20020093762A1:“Method for seed layer removal for magnetic heads,” which is herebyincorporated by reference, presents related concepts of seed andadhesion layer materials and processes.

[0003] The damascene process used herein is described in detail in thecommonly assigned U.S. patent application bearing Ser. No. 10/115,414which is hereby incorporated by reference.

[0004] Commonly assigned U.S. patent application titled “MagneticTransducer with Pedestal Pole Piece Structure” bearing Ser. No.09/884607, which is hereby incorporated by reference, describes atri-layer coil write head embodiment with a pedestal P1 pole piecedefining the zero-throat height which is used in the preferredembodiment of the invention described in this application.

FIELD OF THE INVENTION

[0005] The invention relates to the field of magnetic transducers(heads) having inductive write heads and more particularly to thestructure of and the process for making the pole pieces and coils forthe inductive write head.

BACKGROUND OF THE INVENTION

[0006] A typical prior art disk system 10 is illustrated in FIG. 1. Inoperation the magnetic transducer 20, usually called a “head” isattached to an arm or actuator 13 and flies above the rotating disk 16.A voice coil motor 19 (VCM) pivots the actuator 13 to position themagnetic transducer 20 over selected circumferential tracks on the disk16. The disk 16 is attached to spindle 18 that is rotated by a spindlemotor (not shown). The disk 16 comprises a substrate on which aplurality of thin films are deposited. The thin films includeferromagnetic material that is used to record the magnetic transitionswritten by the magnetic transducer 20 in which information is encoded. Atape based storage system (not shown) uses a magnetic transducer inessentially the same way as a disk drive, with the moving tape beingused in place of the rotating disk 16.

[0007] The magnetic transducer 20 is composed of elements that performthe task of writing magnetic transitions (the write head 23) and readingthe magnetic transitions (the read head 12) as illustrated in FIG. 2.The electrical signals to and from the read and write heads 12, 23travel along conductive paths (leads) (not shown) which are attached toor embedded in the actuator 13. Typically there are two leads each 14for the read and write heads 12, 23.

[0008]FIG. 2 is a midline section of one type of prior art magnetictransducer 20A. The components of the read head 12 are the first shield(S1), two insulation layers 107, 109 which surround the sensor element105 and the second shield 104 (P1/S2). This type of magnetic transducer20A is called a “merged head” because the P1/S2 layer 104 serves as ashield for the read head 12 and a pole piece for the write head 23A. Theyoke also includes a second pole piece 103 (P2) which connects withP1/S2 104 away from the air-bearing surface (ABS) at what is sometimescalled the “back gap” (BG). The P2 103 confronts the P1 104 across thewrite gap layer 42 to form the write gap 43 at the ABS. The coil 37 inthis particular prior art head is deposited on a layer of resist 106which is used to define the zero throat height (ZTH) by forming a stepon the gap layer 42.

[0009]FIG. 3 is a midline section of a second type of prior art magnetictransducer 20B. There are two significant differences between themagnetic transducers 20A and 20B in FIGS. 2 and 3. One difference isthat the yoke in magnetic transducer 20B includes three pole pieces P1104, P2 103A and P3 103B. The P2 103A is formed at the write gap 43 aseparate element. The third pole piece 103B (P3) is stitched to P2 103Aand is connected to the P1 104 at the back gap (BG) to complete theyoke. Typically write heads 23 only have one coil layer 37, but theparticular write head 23B shown has two coil layers which be calledcoil1 37 and coil2 57. The turns of both coil1 and coil2 are routedbetween the write gap 43 and the back gap (BG) and then around behindthe yoke. Coil1 and coil2 are connected electrically (typically behindthe back gap) to form a single inductive coil. The P3 103B arches overthe resist mound 111 which surrounds the coil(s). In either of the priorart write heads 23A, 23B the angle at which the bottom surface of P2moves away from the ZTH point is typically far less than 90 degreeswhich results in efficiency losses through flux leakage.

[0010] In either of the prior art heads 20A, 20B of FIGS. 2 and 3additional coil layers can formed on top of the previous coils prior toforming the enclosing pole piece. Thus, three or more coil layers can bemade within these basic designs. Adding additional coil layers, however,will not change the fundamental limitations on the yoke lengths in theseheads.

[0011] As the required recording densities increase the width of thewritten track must decrease. The needed write heads must have highmagnetic efficiency and low inductance. These requirements make itnecessary to place the inductive components ever closer to the pole tipsthan is possible using the prior art.

[0012] In U.S. Pat. No. 6,194,323 to Downey and Yen, a process formaking semiconductors is disclosed that uses a so-called hard mask. Thehard mask is selected to be more resistant to the metal etchant beingused, which in turn allows a thinner photoresist to be used with aresulting increase in resolution. The hard mask is deposited on themetal layer and a thin photoresist is deposited on the hard mask andpatterned in the convention manner. The hard mask is then etched toexpose portions of the metal layer that can then be etched to achievethe desired pattern of metal. The materials useful for the hard mask aresaid to include titanium nitride, silicon nitride, tungsten, titanium,various glasses, tantalum oxide, aluminum oxide, titanium oxide, as wellas, organic hard masks such as spin-on anti-reflection coatings.

[0013] One process for forming a pattern of material with submicrondimensions is called the damascene process. In this method the patternis developed by etching away selected dielectric material to formfeatures (vias, troughs, etc.) that are then overfilled byelectroplating a metal such as copper. The overfill is removed bychemical-mechanical polishing (CMP) leaving the metal and dielectricmaterial forming the pattern. Hard masks have been used to improve theprecision of the damascene process. In U.S. Pat. No. 6,121,150 Avanzinoand Wang suggest use of sputter-resistant materials for the hard mask.Specifically, they teach the use of high atomic mass metallic materialssuch Ta, W, Ti, TaN, WN and TiN for the hard mask in a damascene processfor fabricating semiconductors.

SUMMARY OF THE INVENTION

[0014] Applicants disclose a method for producing a magnetic transducerwith a inductive write head having a multilayer coil with a high aspectratio and a short yoke. A damascene process is used for two coil layersand a conventional process for the third coil layer. The process of theinvention allows a seed layer for the coil to be deposited on the sidewalls of the trenches for the first and second coil layers. In oneembodiment the seed layer for the coil is preceded by an adhesion layer.

[0015] In a preferred embodiment of the invention the first coil layeris formed below the gap layer and behind a pedestal pole piece for P1. Alayer of polymeric material is deposited to serve as the bed for theturns of the coil. A layer stack including a hard mask layer followed bya masked photoresist layer defines the coil shape and enables etching(RIE) with a high aspect ratio. Tantalum oxide is preferred as the hardmask material. A seed layer is then deposited over the resultingtrenches. This process results in the seed layer being deposited on thesidewalls as well as the bottoms of the trenches. In an alternateembodiment an adhesion layer may be deposited prior to the deposition ofthe seed layer. Tantalum is the preferred adhesion layer and copper isthe preferred seed layer for the coil. A wet electroplating process ispreferred to deposit the conductive material for the coil on the waferto overfill the trenches. The first coil layer is completed when theoverfill is removed by planarization. The gap layer is then formed. Thesecond layer of the coil is formed above the gap layer and behind the P2pole piece using the same method as was used for the first coil layer.The third coil layer may then be formed by a conventional process. Thewrite head is completed with the formation of the P3 pole piece tocomplete the yoke.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 is a symbolic illustration of a prior art disk drive inwhich the head of the invention can be embodied, showing therelationships between the head and associated components.

[0017]FIG. 2 illustrates a section, perpendicular to the air bearingsurface, of a prior art magnetic transducer with one coil layer.

[0018]FIG. 3 illustrates a section, perpendicular to the air bearingsurface, of a prior art magnetic transducer with two coil layers.

[0019]FIG. 4 illustrates a partially formed section of a magnetictransducer according to the invention, perpendicular to the air-bearingsurface, during fabrication after three subpieces of the first polepiece have been formed. FIG. 4 includes the area in front and back ofthe yoke.

[0020]FIG. 5 illustrates a partially formed section of a transduceraccording to the invention subsequent to FIG. 4 in the fabricationprocess, after the masking layer stack has been formed and etched forthe first coil layer. FIG. 5 and subsequent figures include only thearea between the pole tips and the yoke.

[0021]FIG. 6A illustrates a partially formed section of a transduceraccording to the invention subsequent to FIG. 5 in the fabricationprocess after the seed layer has been deposited for the first coillayer.

[0022]FIG. 6B illustrates an enlarged view of the details of oneembodiment of the seed layer structure 51 as shown in FIG. 6A.

[0023]FIG. 7 illustrates a partially formed section of a transduceraccording to the invention subsequent to FIG. 6 in the fabricationprocess after the conductive material (Cu) has been deposited for thefirst coil layer.

[0024]FIG. 8 illustrates a partially formed section of a transduceraccording to the invention subsequent to FIG. 7 in the fabricationprocess after the surface has been planarized leaving the turns of thefirst coil layer separated.

[0025]FIG. 9 illustrates a partially formed section of a transduceraccording to the invention subsequent to FIG. 8 in the fabricationprocess after the gap layer and the bed for the second coil layer hasbeen formed.

[0026]FIG. 10 illustrates a partially formed section of a transduceraccording to the invention subsequent to FIG. 9 in the fabricationprocess after seed layer deposition, Cu plating and planarization of thesecond coil layer.

[0027]FIG. 11 illustrates a section of a transducer according to theinvention subsequent to FIG. 10 in the fabrication process after thethird coil layer and P3 pole piece have been formed.

DETAILED DESCRIPTION OF THE INVENTION AND THE PREFERRED EMBODIMENTS

[0028] It is conventional for thousands of heads to be manufacturedsimultaneously on a single wafer. For simplicity the following willtypically describe the actions or structures for a single head, but itis to be understood that most of the process steps are performed overthe entire wafer and are, therefore, forming structures for thousands ofheads simultaneously. The invention relates to the write head portion ofthe magnetic transducer and does not place limits on the type of readhead that can be used with it. Typically the read head portion of thetransducer is fabricated first, but transducers with the write headportion fabricated first have been described in the prior art. A writehead according to the invention may be fabricated before or after theread head portion of the transducer.

[0029] The relative sizes of the components shown in the figures are notpresented according to scale, since the large range of sizes would makethe drawing unclear. The relative sizes/thickness of the components areaccording to prior art principles except where noted below. The hatchinglines are not intended to represent the material composition of astructure, but are used only to distinguish structures and aid in theexplanation of the process of making the write head.

[0030] One embodiment of the damascene process as described can besummarized as follows. A polymeric material is deposited on aninsulating layer which may be the substrate. The polymeric materialserves as the fill material between the metallic structures. A layerstack is then deposited to serve the masking function. The layer stackbegins with a dielectric layer, which is also called a hard mask, suchas SiOx. An optional adhesion layer may be placed on the dielectriclayer. A masked photoresist layer is then applied to define the metallicstructures and complete the layer stack. The wafer is then etched by amethod such as reactive-ion etching (RIE) to remove the material fromthe areas from the polymeric material defined for the metallicstructures. A conductive, conformal seed layer is then applied to theetched surface. The bulk metal is deposited in a wet plating processwhich builds a non-conformal film, overfilling the trenches.Chemical-mechanical polishing (CMP) is then used to remove material downthrough the hard mask and to planarize the surface. The result is ametallic pattern surrounded with an insulating material. Aspect ratiosof 7 to 10 may be obtained using this method.

[0031] The process of the invention allows a tri-layer coil to be madewith a higher aspect ratio than the process of the prior art. If thesecond layer of the coil is fabricated with a conventional through-maskmethod, planarization will be disrupted by the coil when fabricating theP2 poletip. On the other hand, if the P2 poletip is fabricated first,then there will be too much redeposition onto P2 during the coil seedlayer removal and P2 disrupts the planarization for the second layer ofthe coil. The process of the invention overcomes these problems.

[0032] Reference is made to FIG. 4 to begin the description of theprocess of making a first embodiment of a write head 23C of theinvention. Prior art materials and techniques have been used to form thestructures shown. The section view is perpendicular to the air bearingsurface (ABS) (not shown) which will be on the left of the figure afterthe wafer is sliced. Only a portion of one transducer relating to thewrite head is shown. The elements for the read head (not shown) will befabricated in coordination with the write head and as noted a pluralityof other transducers (not shown)are being fabricated in parallel on thewafer. The first pole piece (P1) 46A-C has been deposited in threesegments, on a generally planar surface of substrate 42 and is made ofstandard ferromagnetic material. The P1 subpiece 46B will also be calleda “P1 pedestal pole piece” to follow the terminology of commonlyassigned U.S. patent application titled “Magnetic Transducer withPedestal Pole Piece Structure” bearing Ser. No. 09/884,607, whichdescribes the advantages of a pedestal P1 pole piece which includedefining the zero-throat height.

[0033] The upper surface of the wafer which includes the upper surfacesof insulating material 44A, 44B is preferably planarized to establish awell controlled surface for the subsequent formation of the first coil(coil1) (not shown). Achieving the smallest pitch in coil1 requires thatP1 also be planarized. The polymeric insulating material 44A, 44B(preferably hard-bake resist) will serve as the bed for the first coillayer. The thickness of the polymeric insulating material 44A, 44Blimits the height of the coil turns. Insulating layer 45 serves toinsulate the first coil layer from the first segment of P1 46A.Insulating layer 45 is a material such as alumina which will act as astop for the subsequent RIE process.

[0034]FIG. 5 is an enlarged view of the area between the P1 polesubpieces 46B, 46C of FIG. 4 after additional steps in the fabricationprocess have been performed. The portion of the write head 23C behindthe P1 pole subpiece 46C is not shown in FIG. 5 to simplify the drawing.The turns of the coil behind the P1 pole subpiece 46C will be similar tothose shown. FIG. 5 shows the trenches 47 which have been etched throughthe layer stack 48. As noted above, the layer stack 48 includes aplurality of layers (not shown): a dielectric hard mask layer (andoptionally an adhesion layer may be placed on the hard mask layer); anda masked photoresist layer which is used to define the coil turns. Thepreferred material for the dielectric hard mask is tantalum oxide. Priorart dielectric materials such as silicon dioxide may also be used.Applicants have found that tantalum oxide has superior etch resistanceto the RIE process and, therefore, provides increased precision to theresolution. The wafer is etched by a method such as reactive-ion etching(RIE) to remove the material from the trenches 47 defined for thesubsequent metallic structures.

[0035]FIG. 6A illustrates the preferred next step in the process whichis the deposition of a seed layer structure 51. The thickness of theseed layer has been greatly exaggerated in relation to the other films.As will be readily known by those skilled in the art, the seed layerstructure 51 is much thinner than the other layers and if shown to scalewould not be visible. The seed layer structure 51 is shown in FIG. 6Bwhich is an enlarged view of a side wall from FIG. 6A. The seed layerstructure 51 must include at least a seed layer 62, but may also includeadditional layers. The seed layer material is selected using prior artmethods based on the material for the subsequent plated deposition ofthe conductive coil which is preferably copper. If electroplating isused then the seed layer must be conductive. A sputtered layer of coppercan used as the seed layer 62. A preferred process uses the two layersfor the seed layer structure 51 as shown in FIG. 6B. In this embodimentan adhesion layer 61 is deposited prior to the seed layer 62. In thisembodiment a very thin layer of tantalum is sputter-deposited prior tothe layer of copper. Tantalum nitride (TaN) may also be used as theadhesion layer 61. When deposited according to the invention the seedlayer 62 and adhesion layer 61 are deposited on the sidewalls of thetrenches, as well as, the bottoms. This is in contrast to prior artmethods which have seed layer material only at the bottom of the trench.This allows the aspect ratio of the coil to be larger than in the priorart. For example, aspect ratios up to eight (8) are achievable using themethod and materials according to the invention, whereas, aspect ratiosof three (3) are the limit of the prior art. Higher the aspect ratiosallow shorter overall yokes or lower coil resistance with resultingincreases in performance.

[0036] In FIG. 7 the result of wet thin film electroplating the copper53 for the coil is shown. This deposition process allows a nonconformalfilm to be formed overfilling the trenches. At this point CMP is used toplanarize the surface down to the level of the pedestals of insulatingmaterial 44A as shown in FIG. 8. At this point the turns of the firstlayer of the coil (coil1) have been formed by the remaining copper 53 inthe trenches.

[0037] The state of the process shown in FIG. 9 is subsequent to severaladditional process steps after the state shown in FIG. 8. In FIG. 9 agap layer 54 has been deposited on the planarized surface and thenetched to form a via exposing the top of the P1 subpiece 46C. The gaplayer 43 is formed from a dielectric material, for example, aluminawhich is not removed by RIE. The back pole piece of P2 56 has beenformed in the via over the P1 subpiece 46C to continue the continuity ofthe ferromagnetic material comprising the yoke and serve as a back fluxclosure of ferromagnetic material. The front P2 pole piece 55 has beendeposited on the gap layer 54 to confront the P1 subpiece 46A to formthe write gap. The front P2 pole piece 55 extends toward to the back ofthe yoke farther than the pedestal pole piece 46B to allow the ZTH to bedefined by the pedestal pole piece 46B. The bed of insulating material58 for the second layer of the coil (not shown) has been deposited andthe surface has been planarized.

[0038] The process of fabricating second layer of the coil is the sameas for the first layer of the coil. FIG. 10 shows the completed secondlayer of the coil 59 (coil2) after planarization. FIG. 11 shows thecompleted write head with insulating layer 59 deposited over the coil2tops to encapsulate coil3 which can be fabricated by conventional priorart methods. Similarly P3 is formed of ferromagnetic materials accordingto prior art to complete the yoke. The three layers comprising the coilare preferably connected in series.

[0039] Although the invention does not depend on particular dimensions,some comments about the preferred dimensions may be instructive. Forexample, the preferred pitch of the coil turns is from 0.5 to 1.5microns. The height of the first and second coil layers is preferablyfrom 2 to 5 microns. The length of the yoke is from 7 to 15 microns. Thepreferred width of P2 is less than 0.5 microns.

[0040] Other variations and embodiments according to the invention willbe apparent to those skilled in the art which will nevertheless be withthe spirit and scope of the invention.

What is claimed is:
 1. A magnetic transducer with an inductive writehead comprising: a gap layer extending from a write gap toward a back ofa yoke; a pedestal pole piece of ferromagnetic material which is incontact with the gap layer at a write gap, a back surface of thepedestal defining a zero throat height line; a first coil layerincluding a plurality of turns of electrically conductive material whichpass between the pedestal pole piece and the back of the yoke, the turnsof electrically conductive material of the first coil layer beingseparated by insulating material having sidewalls with a first seedlayer thereon; a second coil layer including a plurality of turns ofelectrically conductive material which pass between a P2 pole piece andthe back of the yoke, the turns of electrically conductive material ofthe second coil layer being separated by insulating material havingsidewalls with a second seed layer thereon a third coil layer includinga plurality of turns of electrically conductive material which passbetween a P3 pole piece and the back of the yoke.
 2. The magnetictransducer of claim 1 further comprising an adhesion layer between thefirst seed layer and the insulating material.
 3. The magnetic transducerof claim 2 wherein the adhesion layer is tantalum.
 4. The magnetictransducer of claim 2 wherein the adhesion layer is tantalum nitride. 5.The magnetic transducer of claim 1 wherein the first seed layer iscopper.
 6. The magnetic transducer of claim 1 wherein an aspect ratio ofthe first coil layer is greater than three.
 7. The magnetic transducerof claim 1 wherein an aspect ratio of the first coil layer isapproximately eight.
 8. A disk drive comprising: a disk having a thinfilm of ferromagnetic material on a planar surface of the disk; aspindle rotatably supporting the disk; an actuator supporting a magnetictransducer having an air bearing surface confronting the planar surfaceof the disk; and the magnetic transducer including a write headcomprising: a pedestal pole piece of ferromagnetic material which is incontact with a gap layer at a write gap, a back surface of the pedestaldefining a zero throat height line; a first coil layer including aplurality of turns of electrically conductive material which passbetween the pedestal pole piece and a back of a yoke, the turns ofelectrically conductive material of the first coil layer being separatedby insulating material having sidewalls with a first seed layer thereon;a second coil layer including a plurality of turns of electricallyconductive material which pass between a P2 pole piece at the write gapand the back of the yoke, the turns of electrically conductive materialof the second coil layer being separated by insulating material havingsidewalls with a second seed layer thereon a third coil layer includinga plurality of turns of electrically conductive material which passbetween a P3 pole piece connected to the P2 pole piece and the back ofthe yoke.
 9. The disk drive of claim 8 wherein an aspect ratio of thefirst coil layer is greater than three.
 10. The disk drive of claim 8wherein an adhesion layer is disposed between the first seed layer andthe insulating material.
 11. The disk drive of claim 10 wherein theadhesion layer is tantalum.
 12. The disk drive of claim 10 wherein theadhesion layer is tantalum nitride.
 13. The disk drive of claim 8wherein the first seed layer is copper.
 14. The disk drive of claim 8wherein an aspect ratio of the first coil layer is greater than three.15. The disk drive of claim 8 wherein an aspect ratio of the first coillayer is approximately eight.